Remove extracellular cells after antibody opsonization

Hi all,I'm doing a phagocytosis assay with J774 macrophage-like cell line and Cryptococcus neoformans (a yeast). The yeasts are opsonised using specific monoclonal antibody before proceeding to the phagocytosis assay. After 2 hours incubation, I noticed some extracellular yeasts remains attached outside J774 cells even after extensive washing with PBS. Are there any ways I can remove these extracellular yeasts without disrupting the macrophages?Many thanks in advance!